I. Technical Field
THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCT INTERNATIONAL APPLICATION PCT/JP2009/004682.
II. Description of the Related Art
Recently, as a color display device capable of achieving a large screen, thinning, and lightness in weight, a plasma display panel (hereinafter referred to as “PDP”) has received attention.
An AC surface discharge type PDP typical as a PDP has many discharge cells between a front substrate and a rear substrate that are faced to each other. The front substrate has the following elements:                a plurality of display electrode pairs disposed in parallel on a glass substrate; and        a dielectric layer and a protective layer for covering the display electrode pairs.Here, each display electrode pair is formed of a pair of scan electrode and sustain electrode. The protective layer is a thin film made of alkaline earth oxide such as magnesium oxide (MgO), protects the dielectric layer from ion spatter, and stabilizes the discharge characteristic such as discharge start voltage. The rear substrate has the following elements:        a plurality of data electrodes disposed in parallel on a glass substrate;        a dielectric layer for covering the data electrodes;        mesh barrier ribs disposed on the dielectric layer; and        phosphor layers disposed on the surface of the dielectric layer and on side surfaces of the barrier ribs.The front substrate and rear substrate are faced to each other so that the display electrode pairs and the data electrodes three-dimensionally intersect, and are sealed. Discharge gas is filled into a discharge space in the sealed product. Discharge cells are disposed in intersecting parts of the display electrode pairs and the data electrodes. In the PDP having this structure, ultraviolet rays are emitted by gas discharge in each discharge cell. The ultraviolet rays excite respective phosphors of red, green, and blue to emit light, and thus provide color display.        
A subfield method is generally used as a method of driving the PDP. In this method, one field period is divided into a plurality of subfields, and the subfields in which light is emitted are combined, thereby performing gradation display. Each subfield has an initializing period, an address period, and a sustain period. In the initializing period, initializing discharge is caused in each discharge cell, and wall charge required for a subsequent address operation is formed. In the address period, address discharge is selectively caused in a discharge cell to perform display, and wall charge required for a subsequent sustain discharge is formed. In the sustain period, sustain pulses are alternately applied to the scan electrodes and the sustain electrodes, sustain discharge is caused in the discharge cell having undergone address discharge, and light is emitted in the phosphor layer of the corresponding discharge cell, thereby performing image display.
In such a PDP, when the size between the barrier ribs is decreased in order to respond to improvement in definition or the panel is enlarged in order to enlarge the screen, influence such as distortion of the glass substrate increases. Therefore, it is difficult to accurately apply phosphor paste between the barrier ribs. As a result, the phosphor paste adheres to the tops of the barrier ribs or different phosphor pastes come between adjacent barrier ribs, thereby causing a problem of color mixing.
Therefore, an ink jet method allowing accurate application is disclosed (Unexamined Japanese Patent Publication No. 2005-71954). In this method, a phosphor is dispersed in an organic solvent, and ink of viscosity of 10 cP or lower, for example, is produced and delivered from the head tip of the ink jet. Therefore, this method allows position control during application, and can respond to fining of the gaps between the barrier ribs and distortion of the glass substrate.
When a phosphor is formed in such a method, however, a problem is found that many pore parts existing on or in the barrier ribs cause variation in adhering amount of the phosphor adhering to the wall surfaces of the barrier ribs.